[kijiki]

320x200 at 256 colors. X doesn't support any depth lower than 8bit, so VGA 640x480 wouldn't work.

[maximilianburke]

X absolutely supports depths of 1 and 4 bits per pixel, along with 8bpp, with its VGA server: https://www.xfree86.org/4.8.0/vga.4.html

[kijiki]

Thanks for the correction.

I hadn't thought of 1bpp because it isn't interesting on VGA hardware. But you're absolutely right about 4bpp having been a thing.

[mjg59]

X does, modern X apps may not.

[Zardoz84]

I remember that Xfree86 allowed 1 bit (B&W) modes